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https://issues.apache.org/jira/browse/HDFS-11622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15967360#comment-15967360
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Masatake Iwasaki commented on HDFS-11622:
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Thanks for the comment, [~apurtell]. Considering batching in the HBase WAL,
HDFS needs feature to add parent span when {{DFSOutputStream#write}} is called
to append each WALEntry (and when {{hflush}} is called too?). Even code in
trunk does not have this yet. Parent spans added only on queuing DFSPacket now.
The issue described here is about tracking tracing spans by not parent-child
relationship but trace id . This is relevant to branch-2.7 only. While this is
not crucial for end-to-end tracing of HBase WAL batching, I welcome the patch
to fix this issue if there are needs for analyzing tracing spans by trace id
only.
> TraceId hardcoded to 0 in DataStreamer, correlation between multiple spans is
> lost
> ----------------------------------------------------------------------------------
>
> Key: HDFS-11622
> URL: https://issues.apache.org/jira/browse/HDFS-11622
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: tracing
> Reporter: Karan Mehta
>
> In the {{run()}} method of {{DataStreamer}} class, the following code is
> written. {{parents\[0\]}} refer to the {{spanId}} of the parent span.
> {code}
> one = dataQueue.getFirst(); // regular data packet
> long parents[] = one.getTraceParents();
> if (parents.length > 0) {
> scope = Trace.startSpan("dataStreamer", new TraceInfo(0,
> parents[0]));
> // TODO: use setParents API once it's available from HTrace
> 3.2
> // scope = Trace.startSpan("dataStreamer", Sampler.ALWAYS);
> // scope.getSpan().setParents(parents);
> }
> {code}
> The {{scope}} starts a new TraceSpan with a traceId hardcoded to 0. Ideally
> it should be taken when {{currentPacket.addTraceParent(Trace.currentSpan())}}
> is invoked. This JIRA is to propose an additional long field inside the
> {{DFSPacket}} class which holds the parent {{traceId}}.
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